All-wheel-drive motor vehicles have become popular in situations where traction between the wheels and the road is less than ideal or than desirable. Nonetheless, all-wheel-drive powertrains usually consume more energy due to the transmission of engine output to, for example, both the front axles and the rear axles of a motor vehicle. On the other hand, two-wheel drive powertrains usually are more energy efficient because they only need to transmit the engine output to either the front axles (e.g., front-wheel-drive motor vehicles) or the rear axles (e.g., rear-wheel-drive motor vehicles). Some modern motor vehicles include powertrains that switch between the all-wheel-drive mode and the front-wheel-drive (or rear-wheel-drive) mode to have the benefit of both the conventional all-wheel-drive and the conventional front-wheel-drive (or rear-wheel-drive) powertrains.
Such a powertrains often includes a torque transmission device for distributing power between the front axle and the rear axle to enable the switches between the all-wheel-drive mode and the front-wheel-drive (or rear-wheel-drive) mode. A conventional torque transmission device usually includes a motor driven clutch assembly to engage or disengage the engine output with either the front axles or the rear axles. A conventional motor usually includes a cylindrical stator housing that accommodates a rotor therewithin. Such a cylindrical stator housing has exhibited larger magnitudes of vibration and higher levels of noise when the cylindrical stator housing is subject to some input forces either from external sources or from the operations of the motor itself. Moreover, the space allocated for the motor and other components may be constrained in some modern applications, whereas the output requirements for the motor may nevertheless continue to rise. That is, the power density requirement in some modern applications has continued to rise.
Therefore, what is needed is an improved motor that exhibits lower levels of noise and lower magnitudes of vibration, an improved torque transmission device having the improved motor, and a powertrain including the improved torque transmission device.